Baku are said to have come into this world as mirages, that were once seen only in the Etain desert. They appeared to lost wanderers, leading them to safety in oases. One day a magi attempted an experiment, designed to catch one of these mirages. He pulled the creature fully into this world, and opened a path for others of its kind to follow. The tale is well known, and although many have tried to avoid difficult adventures for eggs by recreating this spell, none have been successful. It is thought that these spells fail because the creatures must come willingly. Few of these baku did, as their nature is to stay only for a short time in one reality. Those that did, however, are invaluable companions to the magi they serve, with the ability to change back into the mirages they once were, though they never fully leave this world.

Baku possess the body of a horse, the mane, tail and paws of a lion, and the face and trunk of an elephant. They are curious to look at, but very powerful, with tusks that can skewer almost anything and valuable magical skills. They can pass between the waking world and the realm of dreams, thus allowing a magi to escape harm or reach places that aren't usually accessible. Sometimes, if you just glance at a baku out of the corner of your eye, it seems to be wavering, almost see-through. This is generally a sign of the creature hovering between two worlds. If the bond between a magi and their Baku is very strong, the magi can share the Baku´s dream sight, and see things and even people that are far off. This is an invaluable skill when it comes to wars and discovering what their magi brethren are doing.